<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <meta name="viewport"
        content="width=device-width, user-scalable=no, initial-scale=1.0, maximum-scale=1.0, minimum-scale=1.0">
  <meta http-equiv="X-UA-Compatible" content="ie=edge">
  <title>Title</title>
</head>
<body>
<script>
  let arr = [10, 20, 30]
  // console.log(arr[Symbol.iterator]) // 检测是否有遍历接口
  // let k = arr.keys()
  // console.log(k.next())
  // console.log(k.next())
  // console.log(k.next())
  // console.log(k.next())
  for (let attr of arr) {
    console.log(attr)
  }

  // 可以使用for of 的有 数组、类数组（document.getElementsByTagName('*')）、set、map
</script>
</body>
</html>